Target and circuit



D. SCHULMAN Nov. 26, 1963 TARGET AND CIRCUIT Filed March 15, 1962 FIG. I

mg n \o E /u \2- g L L J F n Tuvimzou AMPLIFIER RECORDER 2o POWER 0R lNDlGATOR SUPPLY DANIEL SOHULMAN INVENTOR ATTORNEY United States Patent search, Inc., Livingston, N.J., a corporation of New Jersey Filed Mar 15, 1962, Ser. No. 179,975 7 Claims. (Cl. 273-1022) This invention relates to a target and circuit for electrically recording projectile perforations which may be produced by projectiles from manually operated firearms. The invention has particular reference to a low cost target which can be used many times without destroymg its usefulness.

Many targets have been designed and made for recording the results of gun fire such as manually held rifles and pistols. Various types of recording circuits have been used with these targets for recording the hits of the projectiles. Many prior targets have been complicated and costly and all of them depending upon a connection between two electrodes made by the projectile, itself. These targets have not always worked with com plete satisfaction because the bullet sheath cannot be relied upon to produce conduction and is often coated with oils and greases from the gun.

The present invention uses electrodes which are formed with long cellulose fibers impregnated with a conducting material. When the projectile perforates the target, the fibers from one electrode make contact with the fibers of the other electrode and a momentary contact is established. This contact produces a very short voltage pulse which is amplified and transmitted to a monostable multivibrator which lengthens the pulse and applies it to a recording or indicating device. The circuit is arranged so that the target will be restored to its normal condition in case the fibers of the two electrodes remain connected to each other after the passage of the projectile. The projectile always causes the fibers of the two electrodes to make contact with each other during penetration and after the projectile leaves, the connecting fibers are usually disconnected. However, in case some fibers remain connected, they will be destroyed by heating and the insulation between the two electrodes is maintained.

One of the objects of this invention is to provide an improved target and circuit which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the invention is to reduce the cost of disposable targets.

Another object of the invention is to provide a target and circuit which produces an indication resulting from the penetration of any type of bullet including plastic bullets and other projectiles made of insulating materials or having an insulating coating.

Another object of the invention is to provide a circuit in connection with a target which produces a relatively long pulse for operating a recording machine regardless of the projectile speed.

Another object of the invention is to provide a target which heals or normalizes itself after penetration.

The invention includes a target and circuit for electrically recording projectile perforations. The target includes a fiat supporting insulator made of laminated paper or corrugated board and two electrodes, one on each side of the insulator. Each electrode is composed of a fibrous body impregnated with a conducting material. The circuit comprises a charging circuit for supplying an operating potential to the electrodes and includes a source of potential, such as a battery, a limiting resistor, and a coupling resistor. The circuit also includes a sensing circuit for determining a projectile perforation and 3,112,110 Patented Nov. 26, 1963 ice includes an electron discharge device having a cathode, an anode, and a control electrode, with the cathode and control electrode connected across the coupling resistor. The electron discharge device is coupled to a mono-stable multivibrator for receiving the pulse caused by momentary connection between the electrodes and for producing a longer pulse which is applied to a controlled instrument.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings.

FIG. 1 is a side view of the target.

FIG. 2 is a cross sectional view of a portion of the target, greatly enlarged.

FIG. 3 is a cross sectional view similar to FIG. 2 but showing a projectile penetrating the target.

FIG. 4 is a schematic diagram of connections showing the circuit used in connection with the target.

Referring now to the figures, a target 10 is composed of a supporting insulator 11 covered on each side with an electrode 12 and 13. The supporting insulator may be made of laminated paper but experiments have shown that a corrugated board having an internal corrugation 16 glued to two flat pieces of kraft paper 15 and 14 gives the best results. The electrodes 12 and 13 are made of long fibers compacted together to form a thin sheet. The electrodes are impregnated with a conducting material which may be a plastic composed of powdered carbon or graphite mixed with a binder such as rosin. Each electrode is connected to an external circuit by means of a tab or clamp which may be conductively connected to the electrode at any portion of its area.

Referring now to FIG. 4 the target 10 has one electrode 12 connected through a limiting resistor 18 to the positive terminal of a power supply 20. The power supply may be a battery or any one of a number of conversion units which convert an alternating current to direct current for amplifier use. Various values of voltage may be used in connection with this circuit, the preferred voltage being between 250 and 300 volts. Electrode 12 is also connected through a coupling capacitor 21 to ground and the negative terminal of power supply 20. The second electrode 13 of the target is connected to ground through a coupling resistor 22 and to the control electrode of an electron discharge device 23 in series with a blocking capacitor 24. The usual leak of about 1 megohm 25 is connected between the control electrode and ground. In order to establish a negative bias for the control electrode, the cathode of device 23 is connected through a biasing resistor 26 to ground.

The electron discharge device 23 acts as an amplifier which receives a very sharp electric pulse (shown in circle 27) from the target and transmits that pulse from the anode through a coupling capacitor 28 to the anode of a mono-stable multivibr-ator 30. The mono-stable vibrator circuit includes two triod'es 31 and 32 with the usual coupling circuits between them. Under normal or quiescent conditions triode 31 is non-conducting while triode 32 passes current supplied by the power supply 20 through resistor 33. When a pulse is applied through capacitor 28 to the anode of triode 31, the multivibrator circuit is activated and conduction is transferred from triode 32 to triode 31 thereby making the anode of triode 32 more positive and starting a pulse (shown in circle 34) which is transmitted through capacitor 35 to a thyratron or amplifier circuit 36. This circuit is connected directly to a recorder or indicator circuit 37. If the recorder circuit 37 is sensitive enough, circuit 36 may be omitted and the pulse through capacitor 35 may be applied directly to circuit 37.

The positive potential from power supply 20 is applied over conductor 38 to the anodes of all the triodes and to the electrode 12 through the limiting resistor 18. Other resistors and capacitors may be used by the circuit in order to adjust the multivibrator to its greatest sensitivity. It should be noted that the sensing circuit is connected across coupling resistor 22 in series with the blocking capacitor 24. It will be apparent that a normalizing circuit has been provided which will destroy fibrous connection means between the two electrodes 12 and '13 in case the two electrodes are connected by a few fibers after a projectile 40 has passed through the target. This normalizing circuit may be traced from the positive terminal of power supply over conductor 38, through the limiting resistor 18 to electrode 12 on the target. Then through the fiber short circuit to electrode 13, the coupling resistor 22, and back to the negative terminal of power supply 20. It should also be noted that when the projectile 40 passes through the target and connects the tWo electrodes together, the coupling capacitor 21 discharges through the short circuit and the coupling resistor 22 thereby providing a sharp, high amplitude pulse which is applied to amplifier 23.

The following circuit constants may be used in the circuit shown in FIG. 4 and are illustrative of a specific application of the invention:

Limiting resistor 18 ohms 47,000 Coupling resistor 22 do 100,000 Resistor 25 megohm l Biasing resistor 26 ohms 1,000 Electron discharge device 23 6AV6 Coupling capacitor 21 microfarad .1 Blocking capacitor 24 do .05

From the above description it will be evident that the invention provides a cheap disposable target in connection with a sensitive sensing circuit which not only converts a short sensed pulse into a much longer power pulse but also provides electrical means for healing and normalizing any permanent short circuit caused by a projectile perforating the target.

The foregoing disclosure and drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense. The only limitations are to be determined by the scope of the appended claims.

I claim:

1. A target and circuit for electrically recording projectile perforations therethrough comprising; a fiat supporting insulator composed of laminated paper; an electrode on each side of said insulator, each of said electrodes comprising a fibrous body impregnated with a conducting material; a charging circuit for charging *said electrodes to a direct current potential difference, said circuit including a source of potential, a limiting resistor, and a coupling resistor; a sensing circuit for determining when a projectile perforates the target and connects the two electrodes by joining the fibers of each, said sensing circuit including an electron discharge device having a cathode, an anode, and a control electrode, with the cathode and control electrode connected across said coupling resistor; the anode of said discharge device coupled to a mono-stable multivibrator for activation by the pulse from the discharge device and for producing a longer pulse which is applied to a controlled instrument.

2. A target and circuit as claimed in claim 1 wherein said electron discharge device is normally non-conductive and becomes conductive only when said two are connected.

3. A target and circuit as claimed in claim 1 wherein said charging circuit is also adapted to normalize said target by burning any fibers which connect said electrodes after penetration by the projectile.

4. A target and circuit as claimed in claim 1 wherein said supporting insulator is made of corrugated board having an inner liner of corrugated paper and two outer flat paper faces.

5. A target and circuit 'as claimed in claim 1 wherein said controlled instrument is an electromagnetic counter.

6. A target and circuit as claimed in claim 1 wherein an amplifier is coupled between said controlled instrument and the output of said multivibrator.

7. A target and circuit for electrically recording pr0- jectile perforations therethrough comprising; a flat supporting insulator composed of corrugated cardboard; an electrode on each side of said insulator, each of said electrodes comprising a body of cellulose fibers impregnated with a powdered conducting material and a binder; a charging circuit for charging said electrodes to a direct current potential difference, said circuit including a source of direct current potential, a limiting resistor and a coupling resistor in series; a sensing circuit for determining When a projectile per-forates the target and connects the two electrodes, said sensing circuit including an electron discharge device having a cathode, an anode, and a control electrode, with the cathode and control electrode connected across said coupling resistor; the anode of said discharge device coupled to a mono-stable multivibrator for activation by the pulse from the discharge device and for producing a longer pulse which is applied to a recording instrument through an amplifier.

References Cited in the file of this patent UNITED STATES PATENTS 2,819,084 Brown et a1 J an. 7, 1958 

1. A TARGET AND CIRCUIT FOR ELECTRICALLY RECORDING PROJECTILE PERFORATIONS THERETHROUGH COMPRISING; A FLAT SUPPORTING INSULATOR COMPOSED OF LAMINATED PAPER; AN ELECTRODE ON EACH SIDE OF SAID INSULATOR, EACH OF SAID ELECTRODES COMPRISING A FIBROUS BODY IMPREGNATED WITH A CONDUCTING MATERIAL; A CHARGING CIRCUIT FOR CHARGING SAID ELECTRODES TO A DIRECT CURRENT POTENTIAL DIFFERENCE, SAID CIRCUIT INCLUDING A SOURCE OF POTENTIAL, A LIMITING RESISTOR, AND A COUPLING RESISTOR; A SENSING CIRCUIT FOR DETERMINING WHEN A PROJECTILE PERFORATES THE TARGET AND CONNECTS THE TWO ELECTRODES BY JOINING THE FIBERS OF EACH, SAID SENSING CIRCUIT INCLUDING AN ELECTRON DISCHARGE DEVICE HAVING A CATHODE, AN ANODE, AND A CONTROL ELECTRODE, WITH THE CATHODE AND CONTROL ELECTRODE CONNECTED ACROSS SAID COUPLING RESISTOR; THE ANODE OF SAID DISCHARGE DEVICE COUPLED TO A MONO-STABLE MULTIVIBRATOR FOR ACTIVATION BY THE PULSE FROM THE DISCHARGE DEVICE AND FOR PRODUCING A LONGER PULSE WHICH IS APPLIED TO A CONTROLLED INSTRUMENT. 